Method of recovery from fossil fuel bearing strata



Oct. 30, 1962 w. J. SHIRLEY 3,061,009

METHOD OF RECOVERY FROM FOSSIL FUEL BEARING STRATA Filed Jan. 17, 1958 INVENTOR WILLIAM F SHIRLEY ATTORNEY 3,061,009 METHQD F RECOVERY FROM FOSSIL FUEL BEARING STRATA William J. Shirley, Santa Cruz, Califi, assignor, by mesne assignments, of one-half to Svenska Skifferolje Aktlebolaget, Urebro, Sweden, a corporation of Sweden Filed Jan. 17, 1958, Ser. No. 709,679 16 Claims. (Cl. 16639) This invention relates to methods used in connection with underground heating of fossil fuel bearing strata to recover valuable products therefrom and particularly from such strata as tar sands and oil shales.

One of the methods heretofore used for oil recovery through heating resulting in pyrolysis and/ or distillation of fossils fuels, such as oil shales and tar sands, of which the Athabasca tar sands of Alberta, Canada, are a well known example, consists in underground heating of the fuel-containing strata, as described in a number of patents. In the application of this method to deposits such as tar sands, it has been found that as the temperature gradually rises, before the tar is actually undergoing decomposition, the water, originally filling the pores and cavities of the strata, is vaporized and the water vapor thus formed tends to melt part of the tar and to carry the molten tar in a dispersed form through the pores of the strata to the gas outlets. In some instances these gas outlets may become plugged by the tar-steam dispersion. In other instances, the dispersion may be carried all the way through the collection lines to the condensing equipment, where the dispersion, together with condensed hydrocarbons, originating from other parts of the operating field unit and being in a later stage of heating, results in a mixture, which is difiicult to separate.

Among the objects of the present invention is a method of eliminating these difficulties.

Other and further objects and advantages will appear from the more detailed description given below, it being understood that such more detailed description is given by way of illustration and explanation and not as limiting since various changes therein may be made by those skilled in the art without departing from the scopeand spirit of the present invention.

In accordance with that more detailed description, there is shown illustratively in the drawing, a vertical section through an installation utilized for carrying out the present invention.

The present invention is particularly directed to a method of preventing clogging by tar or other products that deposit in product outlets and product lines in methods of recovering valuable products such as oils from fossil fuel containing strata by heating in situ or underground to produce products which are obtained from later portions of the recovery system and through product outlets. The method consists essentially in the injection as by pumping into each gas outlet before the heating starts, of a certain amount of a liquid such as a relatively light oil, for instance oil recovered in the same operation from another portion of the operating field unit. The primary action of the injected liquid such as oil, is to displace the water, which generally flows into the bore hole, after it is drilled and may fill the annular space between the easing tube of the heater and the wall of the bore hole, and part of which water may be in the pores of the tar sand adjacent to the bore hole. The introduction of the oil thereby forces the water into the formation and thus suppresses the formation of water vapor when heat is supplied. Also some of the supplied heat from the heater is saved because of the lower heat of vaporization of the liquid such as light oil than of water, and can be made useful for the pyrolysis of the tar sand.

3,061,009 Patented Oct. 30., 1962 ice Besides this primary action, the liquid such as light oil also to some limited extent may act as a dissolving and viscosity-reducing agent on the tar in the same way as the condensed vapors, resulting from the distillation and pyrolysis of, for example, the tar sand in later stages of heating as described in a copending application, Serial No. 357,042, now Patent No. 2,914,309; granted November 24, 1959- to G. J. W. Salomonsson, assigned to the assignees of the present specification.

Different actions or functions or effects obtained by the injected liquid, are, as listed in order of importance or degree:

(a) The oil displaces water and thus reduces steam formation (thereby also saving heat).

b) The oil vapors dissolve tar particles in outlets and lines.

(0) The oil dissolves tar in the adjacent parts of the formation creating a low-viscosity solution, which im proves heat transfer from the heater by convection.

The effect of the injected oil may also, to some degree, be due to a change in surface-tensions in the liquid tarliquid Water-steam system. The stability of the tar-steam dispersion is thereby changed. Actually it has been observed that the effect of the oil injection is improved by adding small amounts (a few parts per million) of a commercially available an-tifoarn agent, for instance, a silicone compound, to the oil before the injection.

The method may be applied in the treatment of any fossil fuel containing strata where during heat treatment, deposition of products such as tars, etc., may take place to produce clogging. Such strata include oil shales and tar sands. But the difliculties are particularly pronounced in the treatment of tar sands in situ. The light oil or other liquid injected, maybe introduced prior to any initial heating of the deposit, or simultaneously therewith, or after the heating has started.

Theliquid employed may include any liquid which at least partially volatilizes at the temperatures of heating and which exhibits solvent properties on the products such as tar formed during heating in starting up operations. Such liquids include hydrocarbons, particularly hydrocarbon products produced from such strata, and are specifically illustrated by petroleum distillates relatively light oils, other hydrocarbon distillates etc.

The liquid employed will generally be an oil, mainly consisting of hydrocarbons within a boiling range of l50-600 F. and with a range of specific gravity from 0.70 to 0.97. The oil may be a paraffin-base, naphthenebase or asphalt-base type oil. It may be crude petroleum or an oil, recovered from the process itself or a distilled and/or refined product or fraction obtained from any of these stated sources.

The heat input per hour is generally the same while the injected oil is exhausted, as it is later. The temperatures in the adjacent parts of the formation rise gradually from the moment the heating starts to the moment the heating ends. As the oil is injected before the heating starts, the formation temperatures are fairly low, while oil is present in the Well and the formation. No substantial part of the formation reaches temperatures above 600 F. while the oil is still present in the well and the formation.

Any type of equipment may be used, which creates the necessary pressure to inject the oil, for instance a pump, or an open tank, with a liquid level, high enough to create a static pressure, or a closed tank connected to a compressed air line.

The drawing shows in a vertical view an illustrative installation wherein 1 represents the tar sand layer, carrying overburden 2. Casing tube 3 for heater 4 is placed within the borehole having wall 5. Gas outlet pipe 6 is sealed in position in the borehole by packer 7 above which cement 8 is placed. Valve 9 is provided on gas outlet .pipe 6. Annular space 10 between casing tube 3 and wall of the borehole contains water up to level 11.

In starting an operation, an oil line from a tank or pump (not shown) is desirably connected to gas outlet 6. After the desired amount of oil has been injected a valve in the line is shut off. Gradually, as the oil displaces the water, the pressure in the line dissipates down to atmospheric pressure. The connection between the gas outlet and the oil line is then broken and gas outlet 6 is connected to a gas line (not shown). The heating is then started as in the following example.

In a tar sand heating operation where the tar content of U116 tar sand is 8% by weight and the thickness of the tar sand layer is 50 feet, the diameter of the bore hole through the strata of tar sand may be 5 inches and the depth may be 70feet from the ground surface. The outer diameter of the casing tube of the heater in the same bore hole may be 2%". In order to fill the annular space between the casing tube and the Wall of the bore hole up to a level, for instance 20 feet below the ground surface a total amount of 24 gallons of oil (sp. 'gr. 0.887) recovered from another part of the same operation where the heat treatment is in a later stage may be injected by means of compressed air with a pressure between 20 and 50 p.s.i. into the hole. .Due to the dissolving and displacing action, another 5 to gallons of oil may be injected, making the total volume of light oil 29 to 34 gallons. The injection desirably takes place immediately before heating starts. If the heat input is 30,000 B.t.u./ hour per heater, the injected oil will generally be vaporized within a few hours, if all heat be used for this purpose. Because of the-heat consumption in the surrounding tar sand and the movement of the oil into the strata, the time for complete vaporization of the oil may be several days, such as 5-20 days. During all of this time there will be enough oil vapors mixed with the outgoing products to prevent clogging in the outlets and in the lines. If necessary, a further injection of oil may be made some days e.g. ten days after the heating started.

'Having thus set forth my invention, I claim:

1. A method for prevention of tar clogging in product outlets and product lines in recovery of oil from fuelcontaining strata by heating in a borehole in situ in said strata which borehole contains water collected from the formation, which consists essentially in introducing hydrocarbon oil liquid under pressure into the borehole sufficient to replace the water in the borehole with hydrocarbon oil liquid introduced, and to drive the water back into the formation, heating the strata through the borehole up to distillation temperature in the presence of vapors of said replacement oil liquid replacing water in the borehole to produce distillation hydrocarbon containing products from the strata, and recovering distillation products.

2. The method of claim 1 wherein the injection takes place before heating has started.

3. The method of claim 2 wherein the strata contain tar sands.

4. The method of claim 2 wherein the strata contain oil shale.

5. The method of claim 1 wherein the injection takes place after heating has started.

6. The method of claim 5 wherein the strata contain tar sands.

7. The method of claim 5 wherein the strata contain oil shale.

8. The method of claim 1 wherein the strata contain tar sands.

9. The method of claim 1 wherein the strata contain oil shale.

10. A method for prevention of tar clogging in product outlets and product lines in recovery of oil from fuelcontaining strata by heating in a borehole in situ in said strata which borehole contains water collected from the formation, which consists essentially in introducing hydrocarbon oil liquid under pressure into the borehole sufficient to replace the water in the borehole with bydrocarbon oil liquid introduced, and to drive the water back into the formation, heating the strata up to pyrolysis temperature in the presence of vapors of said replacement oil liquid to produce pyrolyzed hydrocarbons from the strata and recovering pyrolytic products.

11. The method of claim 10 wherein the injection takes place before heating has started.

12. The method of claim 11 wherein the strata contain tar sands.

13. The method of claim 11 wherein the strata contain oil shale.

14. The method of claim 10 wherein the injection takes place after heating has started.

15. The method of claim 14 wherein the strata contain tar sands.

16. The method of claim 14 wherein the strata contain oil shale.

References Cited in the file of this patent UNITED STATES PATENTS 1,520,012 Conrader Dec. 23, 1924 2,300,348 Dana Oct. 27, 1942 2,423,674 Agren July 8, 1947 2,914,309 Salomonsson Nov. 24, 1959 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No 3,061,009 October 30, 1962 William J, Shirley It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

In. the grant, lines 2 to 4, for "assignor, by mesne assignments, of one-half to Svenska Skifferolje Aktiebolaget, of Orebro, Sweden, a corporation of Sweden," read assignor, by direct and mesne assignments, of one-=half to Husky Oil Company, of Cody, Wyoming, a corporation of Delaware and one half to Svenska Skifferolje Aktiebolaget, of Orebro, Sweden, lines 13 and 14, for "William J, Shirley, his heirs or assigns, and Svenska Skifferolje Aktiebolaget, its successors read Husky Oil Company and Svenska Skifferolje Aktiebolaget, their successors in the heading to the printed specification, lines 4 to 6, for "assignor, by mesne assignments, of one-=half to Svenska Skifferolje Aktiebj olaget, Orebro, Sweden, a corpora tion of Sweden" read assignor, bydirect and mesne assign ments, of one-half to Husky Oil Company, Cody, Wyo,, a corpo ration of Delaware, and one-half to Svenska Skifferolje Aktiebolaget, Orebro, Sweden Signed and sealed this 23rd day of June 1964,

(SEAL) Attest:

ERNEST W, SWIDER Attesting Officer EDWARD J, Brenner Commissioner of Patents 

1. A METHOD FOR PREVENTING OF TAR CLOGGING IN PRODUCT OUTLETS AND PRODUCT LINES IN RECOVERY OF OIL FROM FUELCONTAINING STRATA BY HEATING IN A BOREHOLE IN SITU IN SAID STRATA WHICH BOREHOLE CONTAINS WATER COLLECTED FROM THE FORMATION, WHICH CONSISTS ESSENTIALLY IN INTRODUCING HYDROCARBON OIL LIQUID UNDER PRESSURE INTO THE BOREHOLE SUFFICIENT TO REPLACE THE WATER IN THE BOREHOLE WITH HYDROCARBON OIL LIQUID INTRODUCED, AND TO DRIVE THE WATER BACK INTO THE FORMATION, HEATING THE STRATA THROUGH THE BOREHOLE UP TO DISTILLATION TEMPERATURE IN THE PRESENCE 